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Letter 6937

Becker, L. E. to Darwin, C. R.

14 Oct 1869

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    Sends abstract of her BAAS paper on the role of a parasitic fungus in producing bisexual flowers in Lychnis.

Transcription

28 Jackson's Row | Albert Square | Manchester

Oct. 14. 1869

My dear Mr. Darwin

Will you permit me to send you the enclosed abstract of a paper read at the Exeter Meeting of the British Association, respecting the curious variety of campion flowers I took the liberty of sending you a few years ago, and in which you were good enough to express some interest

If you think the subject worthy of your attention I should be greatly obliged if you would kindly inform me whether you think it possible that the fungus could exert what looks like an ``active coercive force to bend the structure of the flower to its necessities''. From all that I have observed I cannot rest in any other conclusion but in the enclosed abstract, I have merely given the result to which I have been led and not entered into the detailed reasons for it.

If you paid any attention to those plants which I sent you, you may have observed some facts which will bear on this curious question.

On your theory of Pangenesis it seems to me not inconceivable that gemmules of stamens may circulate undeveloped in the pistilliferous plants of campion, and that the presence of the parasite may cause the condition under which these can develop—but without this theory I am totally unable to conjecture in what manner the fungus possibly can cause stamens to grow in a flower that would not naturally have produced them.

Apologising for troubling you with this note I am | yours very truly | Lydia E. Becker

Charles Darwin Esq—



[Enclosure: 1]

<On alteration> in the structure of Lychnis diurna <observed in co>nnection with the development of a <parasitic> fungus

Abstract of Paper read before section D— British Association, Exeter—

Specimens were produced of the common red campion, Lychnis diurna, infested with a parasitic fungus allied to the ``smut'' in wheat which fungus develops its fructification in the anthers of the flower. The campion in its ordinary healthy state has flowers bearing stamens only or pistils only, but about half the plants infested with the parasitic fungus bear flowers containing both stamens and pistils. The writer had never observed bisexual flowers on healthy plants, and attributed the occurrence of that condition in the specimens produced to the action of the parasitic fungus. The diseased plants very rarely produce seed but occasionally late in the season perfect capsules bearing good seed are found on them. A few of the flowers had been submitted to Mr. Darwin, and he had suggested that the pollen being destroyed by the parasite at an early period, the pistil was developed in compensation. But the writer thought that the influence exerted by the parasite was of a much more subtle and surprising character <than this,> and that instead of causing the develop<ment of> a pistil in compensation for destroyed <stamens the> fungus has the power to cause a plant which would naturally have produced pistils only to develope stamens for the accommodation of the parasite— She supposed that the spores of the fungus fell on the stigma of a healthy flower, and infected all the seeds produced by that capsule  that of the plants thus raised all which were naturally male plants remain unaffected in structure by the parasite, but they have their pollen destroyed by it— that all which were naturally female plants would develope their pistils to a certain extent, but as the fungus cannot produce spores without anthers to fructify in a pollen to feed on, it compels the campion to develope these for its accommodation, and the effort of so doing exhausts the forces of the plant, and causes the decay of the capsule, if indeed the previous stunting of the styles does not prevent fertilization. The production of healthy capsules late in the season may be owing to decay in the vigour of the fungus when, the pressure being removed, the plant resumes its natural functions. The fact that only about half the diseased plants are bisexual favours the view that the latter are female plants in which the growth of stamens has been induced by the presence of the fungus—

    Footnotes Add

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    f1 6937.f1
    The abstract appeared in Report of the thirty-ninth meeting of the British Association for the Advancement of Science, held at Exeter (Becker 1869a). CD and Becker had earlier corresponded on the possible dimorphism in Lychnis diurna (now Silene dioica, red campion) and CD had evidently alerted Becker to the fact that a fungus was the cause of the purple anthers she had observed (see Correspondence vol. 11, letter from L. E. Becker, 23--4 May [1863] and n. 5).
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    f2 6937.f2
    Becker refers to plants she sent with her letter of 21 May [1863] (Correspondence vol. 11).
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    f3 6937.f3
    Pangenesis, CD's hypothesis of the transmission and development of hereditary characters, is discussed in Variation 2: 357--404. CD suggested that each individual cell threw off minute particles (gemmules) that circulated in the bodily fluids and were capable of generating new cells, or remaining dormant until required. For more on the relation of the anther-smut fungus to male and female flowers of Silene dioica, see Giles et al. 2006.
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    f4 6937.f4
    The enclosure is damaged. Missing parts have been restored from the published text (Becker 1869a).
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